Auto-generated Email Accounts

If you needed to build functionality in your web app to auto-generate email accounts on your own domain for each user, what approach would you take? Is there a platform (using APIs or no code) that does this well already?

Basecamp and Trello provide this sort of auto-generated email functionality (albeit in a different way) currently:

• https://blog.trello.com/how-to-create-trello-cards-from-email
• https://2.basecamp-help.com/article/211-adding-items-through-email

Here's what I have in mind:

1. Your web app is at mydomain.com
2. A user creates an account, providing their mobile number
3. The app uses an existing no-code platform/API to auto-generate an email address with "countrycodemobilenumber @mydomain.com".
4. The rest of the app does whatever you need it to do.

So that's my question: How would you accomplish steps 1-3 this with no-code tools or an existing API-based platform?